Although the media reports that it is a
proven fact that carbon dioxide (CO2) has caused the warming in the
twentieth century, the fact is that CO2 and earth's temperature are very
poorly correlated (R2=0.44 --
The higher the rs value the greater the
correlation). Most of the temperature increase in the twentieth
century came in the first half of the century, before the industrial
expansion and when CO2 increases were very slow. Conversely, just when CO2
increases really were rising fast, earth's temperatures were actually
declining, not unlike today. It wasn't until the period 1975-2000 that there
was some correlation between CO2 increases and temperature increases.
However, if there was a cause and effect relationship, the correlation
should have been good throughout the entire period. It wasn't. And since
2000, the CO2
levels have continued to go up, while the temperature is going down.

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While the correlation between atmospheric
increases in CO2 and earth's temperatures is poor (r2=0.44, see
above), the correlation
is much better for solar irradiance and solar activity (r2=>70 --
The higher the rs value the greater the
correlation). It has long been known that solar irradiance by itself
does not provide enough energy to cause the warming on earth experienced in
the twentieth century. However, when combined with the type of solar
irradiance that is emitted during periods of high solar activity every 11
and 22 years (the solar cycle), there is a poorly understood, but good
correlation. Solar flares, coronal mass ejections and other solar activity reach a maximum during the peak of each solar cycle and
somehow influence ocean temperatures and therefore climate. One of the
leading theories on this interaction is the interaction between solar
activity and incoming cosmic radiation on cloud formation, explained below.

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Research done primarily at the
Danish National Space
Center has show there is a very high correlation between incoming solar
radiation and cloud formation. Cosmic radiation originates from exploding
super novae. When the cosmic radiation enter the earth's atmosphere, they
excite water vapor molecules, causing them to clump together (condense) into
tiny water droplets which form low elevation clouds. These clouds then
reflect the solar radiation back into space instead of warming the earth.
This causes the earth to cool. When the
sun becomes more active more solar flares,
coronal mass ejections and other solar activity dramatically increase
the solar winds which push back cosmic radiation thereby preventing the
cosmic radiation from reaching the earth's atmosphere and creating more
clouds. Since there is less cloud formation, more solar radiation reaches
the earth's surface and the earth warms. It is estimated that this
phenomenon can account for 85 percent of the warming that occurred in the
twentieth century.

Click on graph to enlarge

There is also a good correlation (R2=.85)
between ocean oscillations and earth's temperature. The Pacific Decadal
Oscillation (PDO) is a warming an cooling of the sea surface temperatures on
a 25-35 year period. It is like the well-known El Niņo and La Niņa cycles,
except they are much longer in duration. In fact, El Niņos are much more
common during the warm phase of the PDO than in a cool phase of the PDO. The
same with the AMO (Atlantic Multidecadal Oscillation), except it is somewhat
longer in its cycle. It is not yet known if the solar causes the PDO and AMO
to shift or if there is no connection. Many scientists argue that the ocean
cycles could be completely independent of the solar cycles. In any event,
the PDO shifted to its cool phase in the late 1990s, which seems to account
for the cooling the earth has experienced since then. The rather strong El
Nino that started in June, 2009, which is uncommon during the cool phase of
the PDO caused a significant jump in earth's temperature. Time will tell
what will happen next. The unfortunate thing is that almost no research
funding (>$4 billion/yr) is going into the solar/ocean effects on earth's
temperature because it is going into CO2 research which has the poorest
correlations.